This project is on the interaction of tumor cells and host defense cells. Current studies include the depression of macrophage chemotaxis that occurs in tumor-bearing patients and experimental animals; the increase in chemotactic and tumoricidal activity that occurs in BCG-infected tumor-bearing mice; the characterization of a chemotactic factor produced by growing tumors in vitro, which could lead to accumulation of macrophages in tumor sites; and the isolation of lymphotoxin, a protein produced by mitogen or antigen-stimulated lymphocytes that is toxic for tumor cells.